<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

</body>
</html>

<script>
  const num = 123456
  let Lists = [123456,654321,456789,987654]
  Lists.splice(Lists.indexOf(num), 1)
  console.log(Lists)
</script>